1. Field of the Invention
This invention relates to an optical element suitable for devices for optical recording, devices for optical display, devices for optical image formation, devices for optical communication, etc.
2. Description of the Prior Art
Various kinds of systems and devices have been proposed having functions such as modulation, deflection or image formation of light flux. For example, a system has been proposed, in which physical changes are generated locally within a medium and the light flux passing through the medium is modulated by the physical changes. For example, Japanese laid-open patent No. 5523/1981 (U.S. Pat. No. 4,281,904) discloses a method for optical modulation, in which an electrical field is applied locally in a crystal comprising an electrooptical material to change the refractive index of the medium at the portion where this electrical field is applied. Also, Japanese patent application No. 128566/1982 (U.S. patent application Ser. No. 516,267, now abandoned) filed by the applicant of the present invention discloses a method for modulating light flux by use of vapor bubbles generated locally in a liquid. Similarly, Japanese patent application No. 179265/1982 (U.S. patent application Ser. No. 539,675, abandoned in favor of continuation application Ser. No. 902,074) discloses a method for modulating light flux by generating a refractive index distribution by locally heating a liquid.